U.S. President Donald Trump (R) looks at Russia's President Vladimir Putin as they take their places for a family photo during the G20 Leaders' Summit in Buenos Aires, on November 30, 2018. (AFP Photo)

MOSCOW, Jan. 9 (Xinhua) -- Kremlin spokesman Dmitry Peskov said Wednesday that he is unaware of a plan to exchange the suspected U.S. spy Paul Whelan for the Russian agent Maria Butina, who is being detained in the United States.

"I have not heard any statements about this and so I can't say anything," Peskov told reporters commenting on media speculations about the possible exchange.

But he noted that Moscow never uses people as "pawns" in a diplomatic game.

"Russia conducts counterintelligence activity against those who are suspected of espionage. This is done on a regular basis," he said.

Whelan, a U.S. national, was detained on Dec. 28 in Moscow on suspicion of espionage. On Dec. 31, the Russian Federal Security Service said it had initiated a criminal case against him.

It was discovered later that Whelan also held a Canadian, a British and an Irish passport.

Whelan's family was quoted by media as saying that the 48-year-old former U.S. Marine traveled to Moscow to attend a friend's wedding.

The incident came after Butina pleaded guilty in a Washington court on Dec. 13 to a single conspiracy charge, admitting that she had acted as an unregistered foreign agent to advance Moscow's interests.

The Russian Foreign Ministry said that Butina was "literally compelled to admit to absolutely absurd charges" due to unbearable conditions created for her in a U.S. prison.

It said Moscow regarded Butina as a political prisoner and would continue working on her release and return home.